GraphicsPath.IsVisible(): Unexpected Results

Martijn Mulder

/*
GraphicsPath.IsVisible() gives unexpected results. I fill a
System.Drawing.Drawing2D.GraphicsPath-object with PointF-structures
that define the unit-square (0,0), (1,0), (1,1) and (0,1). Then I
test 3 different PointF-structures to see if they fall inside the unit-
square and the results are clearly wrong:

Point(-0.2, -0.2) falls inside the unit square... WRONG!!!
Point(0.2, 0.2) falls inside the unit square...
Point(0.7, 0.7) falls outside the unit square... WRONG!!!

It seems that the float numbers get rounded to the nearest integer, but
that is not what I want.
*/

//class TestGraphicsPath
class TestGraphicsPath
{
//data member graphicspath
System.Drawing.Drawing2D.GraphicsPath graphicspath=new
System.Drawing.Drawing2D.GraphicsPath();
//constructor
TestGraphicsPath()
{
graphicspath.AddLines
(
new System.Drawing.PointF[]
{
new System.Drawing.PointF(0f,0f),
new System.Drawing.PointF(1f,0f),
new System.Drawing.PointF(1f,1f),
new System.Drawing.PointF(0f,1f),
new System.Drawing.PointF(0f,0f),
}
);
TestPoint(new System.Drawing.PointF(-.2f,-.2f));
TestPoint(new System.Drawing.PointF(.2f,.2f));
TestPoint(new System.Drawing.PointF(.7f,.7f));
}
//TestPoint
void TestPoint(System.Drawing.PointF a)
{
System.Console.Write("Point({0}, {1}) falls ",a.X,a.Y);
System.Console.Write(graphicspath.IsVisible(a)?"in side ":"outside ");
System.Console.WriteLine("the unit square...");
}
//Main
static void Main()
{
new TestGraphicsPath();
}
}

/*
____________________
output:

Point(-0,2, -0,2) falls inside the unit square...
Point(0,2, 0,2) falls inside the unit square...
Point(0,7, 0,7) falls outside the unit square...
*/

Nov 2 '06 #1

Bob Powell [MVP]

GraphicsPath objects do indeed convert floats to integers. Oops on the part
of the GDI+ team eh?

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

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"Martijn Mulder" <i@mwrote in message
news:45***********************@news.wanadoo.nl...

/*
GraphicsPath.IsVisible() gives unexpected results. I fill a
System.Drawing.Drawing2D.GraphicsPath-object with PointF-structures
that define the unit-square (0,0), (1,0), (1,1) and (0,1). Then I
test 3 different PointF-structures to see if they fall inside the unit-
square and the results are clearly wrong:

Point(-0.2, -0.2) falls inside the unit square... WRONG!!!
Point(0.2, 0.2) falls inside the unit square...
Point(0.7, 0.7) falls outside the unit square... WRONG!!!

It seems that the float numbers get rounded to the nearest integer, but
that is not what I want.
*/

//class TestGraphicsPath
class TestGraphicsPath
{
//data member graphicspath
System.Drawing.Drawing2D.GraphicsPath graphicspath=new
System.Drawing.Drawing2D.GraphicsPath();
//constructor
TestGraphicsPath()
{
graphicspath.AddLines
(
new System.Drawing.PointF[]
{
new System.Drawing.PointF(0f,0f),
new System.Drawing.PointF(1f,0f),
new System.Drawing.PointF(1f,1f),
new System.Drawing.PointF(0f,1f),
new System.Drawing.PointF(0f,0f),
}
);
TestPoint(new System.Drawing.PointF(-.2f,-.2f));
TestPoint(new System.Drawing.PointF(.2f,.2f));
TestPoint(new System.Drawing.PointF(.7f,.7f));
}
//TestPoint
void TestPoint(System.Drawing.PointF a)
{
System.Console.Write("Point({0}, {1}) falls ",a.X,a.Y);
System.Console.Write(graphicspath.IsVisible(a)?"in side ":"outside ");
System.Console.WriteLine("the unit square...");
}
//Main
static void Main()
{
new TestGraphicsPath();
}
}

/*
____________________
output:

Point(-0,2, -0,2) falls inside the unit square...
Point(0,2, 0,2) falls inside the unit square...
Point(0,7, 0,7) falls outside the unit square...
*/

Nov 2 '06 #2

Martijn Mulder

>GraphicsPath.IsVisible() gives unexpected results. I fill a

>System.Drawing.Drawing2D.GraphicsPath-object with PointF-structures
that define the unit-square (0,0), (1,0), (1,1) and (0,1). Then I
test 3 different PointF-structures to see if they fall inside the unit-
square and the results are clearly wrong:

Point(-0.2, -0.2) falls inside the unit square... WRONG!!!
Point(0.2, 0.2) falls inside the unit square...
Point(0.7, 0.7) falls outside the unit square... WRONG!!!

It seems that the float numbers get rounded to the nearest integer, but
that is not what I want.

<SNIP code example>

GraphicsPath objects do indeed convert floats to integers. Oops on the
part of the GDI+ team eh?

Is this sloppy enough to call it a bug?

Nov 3 '06 #3